1. Field of the Invention
The present invention relates to a switch module with a built-in structure of anti-surge and dual disconnection, particularly to one that has conductive plates disconnecting a series connection and an anti-surge structure disconnecting a parallel connection by insulation elements.
2. Description of the Related Art
FIGS. 1A and 1B disclose a conventional overcurrent protection switch 10 that has plural connecting points arranged in the middle part and comprises a housing 11 with a press button 12 on the top, a first terminal 12a, a second terminal 12b, a third terminal 12c separately arranged at the bottom, and a moving element 14. The first terminal 12a has a bimetal plate 13 and a first contact 131; the second terminal 12b has a second contact 121 corresponding to the first contact 131. The moving element 14 has one end linking the bottom of the press button 12 and the other linking the moving terminal of the bimetal plate 13, whereby the pressing of the press button 12 actuates the first contact 131 connecting to the second contact 121 and therefore turns on the device; while overcurrent occurs, the bimetal plate 13 deforms due to high degree of temperature and disconnects the first and second contact 131, 121, turning off the device so as to form an overcurrent protection switch 10. Such structure can be found in Taiwan patent applications No. 540811, 367091, 320335, 262168, and 208384. However, the structure disclosed above aims at protection from overcurrent situation but is not able to protect the device when sudden overvoltage such as lightning strike occurs.
Therefore, for safety concern, a usual solution to the defect is to parallel connect to a metal oxide varistor, and to connect to a thermal fuse in series.
FIG. 2A is the invention of U.S. Pat. No. 8,643,462. It discloses an anti-surge switch module applied in an electric system. The switch module comprises a power switch 105, an insulating member 106, a surge absorber 107 and a pyrocondensation belt 108. The insulating member 106 engages with the power switch 105 that abutting against the surge absorber 107; and the pyrocondensation belt 108 ties the surge absorber 107 and the insulating member 106 together so that it could contract when receiving the heat from the surge absorber 107 and thus turn off the power switch 105 under certain degree of contracting. However, the insulating member 106, the surge absorber 107 and the pyrocondensation belt 108 are not disposed inside the power switch 105 but are connected outside, failing to form a complete device with the power switch 105.
In short, the structures disclosed above have shortcomings as uncertain quality, possible exceeding heat due to external connection of components, slow reaction, large volumes, and complicated composition, and they require more constructing space and procedures. Besides, the protection device has to be connected independently outside instead of having one inside.
In UL 1449 3rd Edition (2009) Type 4 was added to Surge Protective Devices (SPDs) requirements. The 3rd Edition also includes the Low voltage Surge Arresters under 1000V in the requirements, and the title is also altered from Transient Voltage Surge Suppressors into Surge Protective Devices. This shows the importance of integrating the components and the surge arresters function of the device.
Hence, the inventor has an invention in U.S. patent application Ser. No. 14/617,000 filed on Feb. 9, 2015 which has an anti-surge disconnection structure built inside a heat-resisting and fireproof housing of an overcurrent protection switch so that the disconnection could be operated successfully and instantly when an overload occurs. Features of the invention disclosed are illustrated in FIG. 2B. A band 74 having a first end 741 and a second end 742 fixedly adhered on a surface of a metal oxide varistor 71 by a thermo-sensitive piece 72 to have the band 74 tightly compressing a spring 73 by wrapping it up. When overvoltage occurs, the metal oxide varistor 71 heats up and melts down the thermo-sensitive piece 72 instantly and therefore loosens the band 74 for the spring 73 to eject upwards to push a pushing rod 75 and disconnect the circuit.
Still, the inventor has continued to develop such feature and further designed a switch module disclosed in U.S. patent application Ser. No. 14/950,069 filed on Nov. 24, 2015. The switch module has provides the same effect in operation as the previous one. The invention also has a built-in structure that can melt down a thermo-sensitive piece by a heating metal oxide varistor for a spring element to be loosened and has an outer periphery thereof displacing a pushing rod, so as to detach a first contacting point from a second contacting point, thus disconnecting the circuit. However, both inventions can only disconnect the circuit of series connection, but cannot ensure the structure therein is completely disconnected. That is, the outer periphery of the spring element would still contacting surfaces of the metal oxide varistor; and if the entire structure cannot be disconnected thoroughly, the circuit may still be working and keep heating up, resulting in a dangerous situation.
On the other hand, metal oxide varistors are prone to operate function less effectively after in use for a period. To overcome such issue, manufacturers usually have a fuse connected to a metal oxide varistor for safety concerns, and the inventor therefore tries to improve such structure with a simpler and easier manufacturing process and better effectiveness based on structures of the previous inventions mentioned above.